A fluorinated copolymer is excellent in heat resistance, flame retardance, chemical resistance, weather resistance, non-tackiness, low friction property and low dielectric property. It is, therefore, used in a wide range of fields including e.g. a coating material for heat-resistant non-flammable electric wires, a corrosion-resistant piping material for chemical plants, an agricultural plastic greenhouse material, a release coating material for kitchen utensil, etc.
Particularly, as compared with a partially fluorinated type ethylene-tetrafluoroethylene copolymer (hereinafter referred to also as “ETFE”), a polyfluorinated vinylidene (hereinafter referred to also as “PVdF”), etc., perfluorinated copolymers such as a polytetrafluoroethylene (hereinafter referred to also as “PTFE”) and a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (hereinafter referred to also as “PFA”) are excellent in chemical resistance but are poor in elasticity and abrasion resistance.
It has been tried to improve the abrasion resistance of a perfluorinated copolymer such as PTFE or PFA by forming a polymer alloy of the fluorinated copolymer with another resin so as to be used under an environment in which the abrasion resistance is desired such that the fluorinated copolymer may be contained in an insulating layer for an insulated electric wire.
For example, in the electric wire coating material described in Patent Document 1, a fluorinated copolymer to be contained in the material is formed into a polymer alloy with a thermoplastic resin which is harder than the fluorinated copolymer and is excellent in the mechanical strength in order to improve the abrasion resistance.
On the other hand, it has been desired to reduce the size and weight of vehicle devices, etc. to be used for automobiles, railroads, airplanes, etc. Therefore, it is desired to reduce the thickness of an insulating layer for an insulated electric wire to be used in the vehicle devices.
For example, Patent Document 2 discloses an insulated electric wire having an insulating layer comprising PFA having at least a predetermined value of MFR (abbreviation of Melt Flow Rate) and at least a predetermined content of constitution units based on a perfluoropropyl vinyl ether, whereby the thickness is reduced.